Ignition electrode unit



United This invention relates to ignition devices, and especially toignition electrode units, for gas burners.

Ignition electrode units to which the present invention pertains are ofthe type used especially, though by no means exclusively, in bakeryovens and the like. Accordingly, electrode units of this type arerelatively long so that they may extend from the outside of the oventhrough the heavily insulated and accordingly deep front wall thereof toafford an external terminal connection with wiring, yet provide asparking electrode in igniting proximity with a gas burner in theinterior of the oven. Conventional ignition electrode units of this typecomprise ceramic insulators or end pieces through which extends a longconductor having a wire terminal at one end and carrying a sparkingelectrode at the other end, and a long tubular mounting sleeve which isinterposed between the end pieces and surrounds the conductor. Whileprevious ignition electrode units of this type are satisfactory insofaras their burner igniting performance is concerned, their rigidconstruction gives rise to frequent breakdown or malfunction, dueespecially to ready breakage of the ceramic end pieces by thedifferential expansion of the conductor and mounting sleeve in the* hotoven, with the result that these previous units frequently requirecostly repair or replacement with ensuing temporary loss of ovenperformance.

lt is an object of the present invention to provide an ignitionelectrode unit of this type which is highly eicient and reliable inperformance and, in comparison to prior units, assuredly long-lastingand unaffected by the differential expansion of the conductor andmounting sleeve.

Another object of the present invention is to provide an ignitionelectrode unit of this type with a resilient member, preferably aspring, which takes up the dif ferential expansion of the conductor andmounting sleeve in such wise that the ceramic end pieces are not in anyway subjected to harmful stresses springing from the uneven expansion ofthese parts.

It is a further object of the present invention to provide an ignitionelectrode unit of this type in which the ceramic end pieces are in anexceedingly simple structural manner securely locked to the oppositeends, respectively, of the mounting sleeve against rotation thereonwithout requiring any harmful forced it between these parts.

Another object of the present invention is to provide an ignitionelectrode unit of this type in which the conductor is in an exceedinglysimple structural manner securely locked directly to a ceramic end pieceagainst rotation therein, yet has free axial play therein for thetake-up of the differential expansion of the conductor and mountingsleeve by the before-mentioned spring without exerting the least stresson this or the other ceramic end piece.

It is a further object of the present invention to provide an ignitionelectrode unit of this type in which the ice ceramic end pieces are ofidentical construction, thereby not only reducing the number ofdifferent stock parts for the instant unit, but also greatlyfacilitating the error-less assembly of the parts of the unit.

It is another object of the present invention to provide an ignitionelectrode unit of this type of which the conductor is a single Wire ofuniform cross-section throughout for its ready assembly with the otherparts of the. unit, and carries at one end beyond the adjacent ceramicend piece a collar for lengthwise adjustable safe mounting therein ofthe sparking electrode by a readily accessible set screw in the collar.

A further object of the present invention is to provide an ignitionelectrode unit of this type of which the parts .i are few in number andof exceedingly simple construction, and lend themselves to quickassembly by eicient mass production methods at very low cost and withoutrequiring any special skill, and to equally quick disassembly for therepair or replacement of any part thereof if necessary.

Further objects and advantages will appear tok those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

Fig. l is a perspective view of an installed ignition electrode unitembodying the present invention.

Fig. 2 is an enlarged longitudinal section through the installedignition electrode unit, taken substantially on the line 2 2 of Fig. l;

Fig. 3 is an enlarged cross-section through the unit as taken on theline 3 3 of Fig. 2;

Fig. 4 is an enlarged fragmentary longitudinal section through anignition electrode unit embodying a modified form of the presentinvention; and

Fig. 5 is an enlarged fragmentary longitudinal section through anignition electrode unit embodying another modified form of the presentinvention.

Referring to drawings, and more particularly to Fig. l thereof, thereference numeral it! designates an ignition electrode unit which isshown installed, in the present instance, in the front wall of a bakeryoven or the like. The front wall of the oven comprises outer and innerwalls 12 and 14, respectively, and the space therebetween is usuallyfilled with suitable heat-insulating material (not shown). interposedbetween the outer and inner oven walls 12 and 14 is a sleeve i6 throughwhich to introduce into the interior of the oven the instant electrodeunit 10 as well as a gas supply pipe 18 for a gas burner unit 2t) havingthe flame side 22. The outer ends of the gas supply pipe 18 andelectrode unit l@ are suitably mounted in a cover plate 24 on the outeroven wall 12. rThus,

the outer end of the electrode unit 10 may removably be mounted in thecover plate 24 by means of a set screw 26 (see also Fig. 2). The innerend of the electrode unit 10 may conveniently be secured to the burnerunit 2t) by means of a strap 28. The cover plate 24 is preferably alsoprovided with a peephole which is normally closed by a pivoted cover 3%.rhe cover Si) may be turned into open position to observe through thepeephole which is normally closed by a pivoted cover 39. The cover 30may be turned into open position to observe through the peephole theignition of the burner unit 20 at the flame side 22 thereof, as well asthe ames themselves for their possible regulation if necessary. The tip32 of the sparking electrode 34 of the ignition unit 10 is in thisinstance shown somewhat bent into proximity to the flame side 22 of theburner unit 2i), and the strap 2S may conveniently be interrupted at 36so that the sparking action of the electrode tip 32 may be observedthrough the peephole in the cover plate 24.

As shown in Fig. 2, the ignition electrode unit 10, hereinaftersometimes referred to as unit, comprises two preferably cylindrical endpieces 38 and 4t) of heatresistant and electrically non-conductiveceramic material, an electrical conductor 42 in the form of a singlewire of uniform cross-section throughout, and an outer tubular spacersleeve 44 of steel or any other suitable heatresistant material betweenthe ceramic end pieces 38 and 49. The end pieces 38 and 40 havediametrically reduced portions 46 and 48, respectively, which arereceived with a sliding fit in the mounting sleeve 44, and the oppositeends of the latter bear against annular shoulders d and 52 on the endpieces 38 and 40, respectively. Extending with a sliding fit throughround holes 54 and S6 in the end pieces 38 and 40, respectively, is theconductor 42. In order to lock the conductor 42 against rotation in theunit 10, the former is provided with one, and preferably twodiametrically opposite keys 58 and 60 which, as shown in Figs. 2 and 3,are received in key ways 62 and 64, respectively, in the ceramic endpiece 46, thus providing a splined connection between the conductor 42and end piece 40. Conveniently, the keys S8 and 60 are simply swagedfrom the solid wire stock of the conductor 42 in the manner bestindicated in Fig. 3.

The opposite end piece 38, though not used in the present instance forlocking the conductor 42 against rotation in the unit 10, isnevertheless provided with the same key ways 62 and 64', and is in allother respects identical with the end piece 46 so that these end piecesmay be used interchangeably.

The conductor 42 may in its inner end press-fittedly or otherwisesecurely receive the sparking electrode 34 which may be an electricalconductor of any suitable, especially heat-resistant metal, such ascommercially known Nichrome, for instance. The conductor 42 is near itsinner end preferably provided with further lateral projections 70 and 72(Fig. 2) which, like the keys 58 and 6i), are conveniently swaged fromthe solid wire stock of the conductor 42, and serve as shoulders to bearagainst a washer 74 on the adjacent end of the ceramic end piece 40.

Surrounding the outer end of the conductor 42 is a preloaded compressionspring 76 which is interposed between a spring-retainer 78 and a washer8f) on the adjacent end of the ceramic end piece 38 (Fig. 2). Receivedon the threaded outer end of the conductor 42 is a suitable terminal 82for wiring w (Fig. l). The terminal 82 serves also to hold thespring-retainer 7 8 in place.

In use, the greater length of the unit is subjected to i construction ofthe unit lt), the differential expansion of the conductor 42 andmounting sleeve 44 fail to set up any stresses whatsoever in the unitlt) and especially in the readily breakable ceramic end pieces 38 and4t), the spring 76 acting to take up the differential expansion of theconductor 42 and mounting sleeve 44 without harm to any of the parts ofthe unit.

ln order to hold the tip 32 of the sparking electrode 34 in ignitingrelation with the flame side 22 of the burner unit 20, it is alsonecessary to lock the ceramic end pieces 38 and 40 against rotation inthe mounting sleeve 44. To this end, the diametrically reduced portions46 and 48 of the end pieces 38 and 40, respectively, are provided withats 86 and 88, respectively, against which the adjacent ends of themounting sleeve 44 are conveniently deformed, preferably in the mannerindicated in Fig. 3. Thus, Lperipherally spaced portions 90 and 92 ofthe originally cylindrical inner end of the mounting sleeve 44 mayconveniently be depressed inwardly to form spaced flat shoulders inengagement or near engagement with spaced portions of the flat 88 on theend piece 40. The outer end of the mounting sleeve 44 may similarly bedeformed to provide flat shoulders in engagement or near engagement withspaced portions of the flat 86 on the end piece 38. Of course, the flatshoulders in the opposite ends of the mounting sleeve 44 are formedtherein prior to the assembly of the latter with the end pieces 38 and40, and care is taken in the assembly of these parts that the ceramicend pieces 38 and 4t) slide freely into locked interengagement with theopposite ends of the mounting sleeve 44 without sustaining any damage.

Fig. 4 shows a modified interlock between a mounting sleeve 44 and aceramic end piece 40. In this case, there is inwardly deformed in themounting sleeve 44' a transverse bead 94 which, in the assembledrelation of the parts 40 and 44', is in engagement or near engagementwith the at 88 on the end piece 40.

Fig. 5 shows another modified form of the invention. In this case, theswaged lateral stop shoulders 70 and 72 near the inner end of theconductor 42 in Fig. 2 are replaced by a suitably secured collar 98which acts as a stop for the conductor and receives a readily accessibleset screw 100 for the lengthwise adjustable mounting of the sparkingelectrode 34' in a bore 102 in the conductor.

The instant ignition electrode unit in its various forms secures severalimportant advantages. Thus, the instant unit has, in comparison toprevious units of this type, an exceptionally long useful life duringwhich it will efficiently and reliably perform its designated functionof igniting a gas burner unit. This is due primarily to the take-up ofthe differential expansion of the conductor and mounting sleeve by thedescribed spring without setting up any stresses whatsoever in thereadily breakable ceramic end pieces. The differential expansion take-upspring further permits the entirely satisfactory, though non-bindinginterlock between the ceramic end pieces and the mounting sleeve on theone hand, and between the ceramic end pieces and the conductor on theother hand, against rotation of these parts relative to each other,without imposing on the ceramic end pieces any strain whatsoever whichmight conceivably lead to breakage of the same. The identicalconstruction of the ceramic end pieces not only reduces the number ofdifferent stock parts for the instant electrode unit, but also greatlyfacilitates the error-less assembly of the parts of the unit to theextent where even unskilled labor will satisfactorily perform the taskof assembling these parts, Thus, regardless of any scheduled mode ofassembling the parts of the instant electrode unit, the assembler need,by virtue of the identical construction of the ceramic end pieces atboth ends of the unit, pay no attention whatsoever to the assembly ofthese end pieces with the mounting sleeve for no possible error canarise from the assembly of these identical end pieces with the mountingsleeve. The preferred and modified forms of the interlock between theceramic end pieces and the mounting sleeve are structurally exceedinglysimple, and so is the specific interlock between the conductor andeither one of the ceramic end pieces. Thus, it is an exceedingly simpleoperation to deform the opposite ends of the mounting sleeve in themanner shown in Fig. 3 or in the manner shown in Fig. 4, and theformation of the keys on the conductor by the simple expediency ofswaging them from the solid wire stock of the conductor is especiallyingenious. Equally ingenious is the molding of the ceramic end pieceswith the key ways, for this involves no greater cost than if they weremolded without key ways. The provision of a collar in one of themodified forms of the electrode unit affords a convenience stop shoulderfor the conductor and a secure mount for a readily accessible set screwwith which to hold the sparking electrode in lengthwise adjustedposition and also against rotation on the unit. The number of parts ofwhich the electrode unit is composed is exceedingly low, and all theparts are simple in construction and readily lend themselves to quickassembly by efficient mass production methods at very low cost andwithout requiring any special skill. The instant electrode unit lendsitself equally Well to quick disassembly of its parts for the repair orreplacement of any part or parts thereof.

The invention may be carried out in other specific ways than thoseherein set forth Without departing from the spirit and essentialcharacteristics of the invention, and the present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

I claim:

1. A long ignition electrode unit for gas burners in bakery ovens andthe like, comprising two apertured ceramic end pieces of which theaperture of at least one end piece has a longitudinal key way; amounting sleeve interposed between and abutting said end pieces andinterlocked with at least said one end piece against rotation relativethereto; an electrical conductor extending through said sleeve withclearance therefrom and being axially slidably received intermediate itsends in the apertures in said end pieces, said conductor having a keyreceived in the key way of said one end piece, and opposite shoulders ofwhich one shoulder engages the outer end of a certain t3 end piece andthe other shoulder is outwardly spaced from the other end piece; and aspring interposed between said other shoulder and other end piece andadapted resliently to hold said end pieces and sleeve in said abuttingrelation and take up all differential expansion of said conductor andsleeve on subjection of the unit to heat.

2. A long ignition electrode unit as set forth in claim 1, in which saidconductor is of solid wire stock, and said key is a swaged projection ofsaid wire stock.

3. A long ignition electrode unit as set forth in claim 1, in which saidconductor is of solid wire stock, and said one shoulder and key areswaged projections, respectively, of said wire stock.

4. A long ignition electrode unit as set forth in claim 1, in which bothof said end pieces are identical and, hence, interchangeable.

References Cited in the le of this patent UNITED STATES PATENTS1,288,898 Hunter Dec. 24, 1918 1,361,688 Courson Dec. 7, 1920 1,647,099MacDonald Oct. 25, 1927 2,545,945 Ensign et al Mar. 20, 1951

